The proposed work investigates the relationship between plasma catecholamines and sensory gating of the auditory P50 wave using the evoked potential. Studies have been designed to evaluate the stability of sensory gating in normal subjects, to follow the effects, in normal subjects, on sensory gating of low dose amphetamines, which are psychotomimetic at high doses, and to correlate sensory gating with plasma catecholamines in psychotic patients. As a group they are designed to investigate the possibility that loss of sensory gating is a final common pathway of psychosis which is permanent in schizophrenics, and temporary in other patient populations and in subjects under the influence of psychotomimetic drugs.